Battery management system for gauging with low power

ABSTRACT

Implementations of fuel gauges may include a voltage sensor coupled with a memory, a processor coupled with the memory, a mode control logic circuit coupled with the voltage sensor, and a sampling timer coupled with the voltage sensor. The memory may include a plurality of relative state of charge (RSOC) values of a battery. The plurality of RSOC values may be used to calculate a plurality of internal resistance values. The fuel gauge may be configured to either increase, decrease, or maintain a sampling frequency based upon a measured power being drawn by a load coupled to the battery.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of the earlier U.S.Utility patent application to Kondo entitled “Battery Management Systemfor Gauging with Low Power,” application Ser. No. 16/366,514, filed Mar.27, 2019, now pending, which application is a continuation-in-partapplication of the earlier U.S. Utility patent application to Kondoentitled “Battery Management System for Gauging with Low Power,”application Ser. No. 16/059,756, filed Aug. 9, 2018, now issued as U.S.Pat. No. 10,423,211, which application was a continuation application ofthe earlier U.S. Utility patent application to Kondo entitled“Variable-Frequency Sampling of Battery Voltage to Determine Fuel GaugePower Mode,” application Ser. No. 14/684,635, filed Apr. 13, 2015, nowissued as U.S. Pat. No. 10,095,297, the disclosures of each of which arehereby incorporated entirely herein by reference.

BACKGROUND

Consumer electronics—such as smart phones, laptops, tablets, videocameras and handheld game consoles—are typically powered by batteries.Such batteries are generally rechargeable while in place within theconsumer electronic device. Various battery systems are designed to becharged and discharged during a number of charging and dischargingcycles.

SUMMARY

Implementations of fuel gauges may include a voltage sensor coupled witha memory, a processor coupled with the memory, a mode control logiccircuit coupled with the voltage sensor, and a sampling timer coupledwith the voltage sensor. The memory may include a plurality of relativestate of charge (RSOC) values of a battery. The plurality of RSOC valuesmay be used to calculate a plurality of internal resistance values. Thefuel gauge may be configured to either increase, decrease, or maintain asampling frequency based upon a measured power being drawn by a loadcoupled to the battery.

Implementations of fuel gauges may include one, all, or any of thefollowing:

The fuel gauge may be configured to either increase or decrease thesampling frequency from either a zero sampling frequency, a low samplingfrequency, a medium sampling frequency, or a high sampling frequency.

The plurality of RSOC values may be derived using a Coulomb countingmethod.

The plurality of RSOC values may be derived using a voltage trackingmethod.

The plurality of internal resistance values may be calculated using atemperature of the battery.

The voltage sensor may be configured to repeatedly sample the measuredpower being drawn by the load from the battery at a sampling frequencycorresponding to the power mode of the fuel gauge using the samplingtimer.

The fuel gauge may be configured to compare a fluctuation between aplurality of measured power values to one or more threshold valuesderived from the plurality of RSOC values.

The fuel gauge may include a fluctuation monitor block coupled to thevoltage sensor.

Implementations of fuel gauges may include a voltage sensor coupled witha memory, a processor coupled with the memory, a mode control logiccircuit coupled with the voltage sensor, a temperature sensor coupledwith the memory, and a sampling timer coupled with the voltage sensor.The memory may include a plurality of relative state of charge (RSOC)values and a plurality of temperature parameters of a battery. Theplurality of RSOC values and the plurality of temperature parameters maybe used to calculate a plurality of internal resistance values. The fuelgauge may be configured to either increase, decrease, or maintain asampling frequency based upon a measured power being drawn by a loadfrom the battery.

Implementations of fuel gauges may include one, all, or any of thefollowing:

The fuel gauge may be configured to either increase or decrease thesampling frequency from either a zero sampling frequency, a low samplingfrequency, a medium sampling frequency, or a high sampling frequency.

The plurality of RSOC values may be derived using a Coulomb countingmethod.

The plurality of RSOC values may be derived using a voltage trackingmethod.

The voltage sensor may be configured to repeatedly sample the measuredpower being drawn by the load from the battery at a sampling frequencycorresponding to the power mode of the fuel gauge using the samplingtimer.

The fuel gauge may be configured to compare a fluctuation between twomeasured power values to one or more threshold values derived from theplurality of RSOC values.

Implementations of a method of conserving power may include sampling atleast two measured power values of a battery using a voltage sensorcoupled with a sampling timer, determining a fluctuation between the atleast two measured power values, comparing the fluctuation between theat least two measured power values to one or more threshold powermeasurements. The one or more threshold power measurements may bederived from a table of values corresponding with a plurality ofrelative state of charge (RSOC) values of the battery. The method mayalso include using the fluctuation between the at least two measuredpower values, sending a signal to a mode control logic circuit to eitherincrease, decrease, or maintain a sampling rate of the fuel gauge.

Implementations of the method for conserving power may include one, all,or any of the following:

The method may include sensing a temperature of the battery through atemperature sensor included in the fuel gauge.

The temperature of the battery may be used to calculate the one or morethreshold power measurements.

The RSOC values may be generated through a Coulomb counting method.

The RSOC values may be generated through a voltage tracking method.

The sampling frequency may include either a zero sampling frequencymode, a low sampling frequency mode, a medium sampling frequency mode,or a high sampling frequency mode.

The foregoing and other aspects, features, and advantages will beapparent to those artisans of ordinary skill in the art from theDESCRIPTION and DRAWINGS, and from the CLAIMS.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations will hereinafter be described in conjunction with theappended drawings, where like designations denote like elements, and:

FIG. 1 is a front view of an illustrative electronic device;

FIG. 2 is a block diagram of at least some components within anelectronic device;

FIG. 3 is a block diagram of at least some components within a fuelgauge of the electronic device;

FIG. 4 is a graph illustrating a variable frequency voltage samplingscheme;

FIG. 5 is a flow diagram of an illustrative method usable to implementthe techniques disclosed herein;

FIG. 6 is a block diagram of select components within an electronicdevice;

FIG. 7 is a graph illustrating a variable frequency voltage samplingscheme as it relates to a battery's internal resistance and voltagefluctuation;

FIG. 8 is a diagram representing the voltage fluctuation of a system;

FIG. 9 is a block diagram of select components within a fuel gauge of anelectronic device;

FIG. 10 is a graph showing internal impedance of a battery;

FIG. 11 is a graph showing varying internal impedance of a battery;

FIG. 12 is a graph showing how internal impedance of a battery isaffected by temperature;

FIG. 13 is a flow chart illustrating how threshold values aredetermined; and

FIG. 14 is a flow chart illustrating how the sampling frequency isdetermined.

DESCRIPTION

Disclosed herein are methods and systems for variable-frequency samplingof an electronic device battery voltage to determine a fuel gauge powermode. An illustrative electronic device implementing the techniquesdisclosed herein contains a battery supplying power to the components ofthe electronic device and a fuel gauge that monitors the battery. Thefuel gauge is capable of operating in numerous power modes (e.g.,standby mode, relaxed mode, operating mode, active mode), each one ofwhich causes the fuel gauge to consume different amounts of power. Thefuel gauge selects its power mode based on a sampling of the voltageprovided by the battery. The fuel gauge samples this voltage at avariable frequency, with the precise frequency depending on the powermode in which the fuel gauge is currently operating and changing as thefuel gauge power mode changes. Based on the voltage swings betweensamples and on how often the voltage changes, the fuel gauge eitherswitches to a lower power mode, stays in its currently-enabled powermode, or switches to a higher power mode.

For example, while the fuel gauge is in a standby mode, it may samplethe battery voltage once per minute; in a relaxed mode, once every 20seconds; in an operating mode, once every 10 seconds; and in an activemode, four times per second. If, while in any of these power modes, thefuel gauge consecutively samples the battery voltage a predeterminednumber of times and determines that there is no voltage change, the fuelgauge autonomously switches to a lower power mode (unless the fuel gaugeis already in the lowest available power mode, such as a standby mode).If the fuel gauge consecutively samples the battery voltage thepredetermined number of times and determines that there is at least onevoltage change but that the greatest voltage change (in eitherdirection) fails to meet or exceed a voltage change threshold, the fuelgauge remains in its currently-enabled power mode. Similarly, if thefuel gauge consecutively samples the battery voltage the predeterminednumber of times and determines that there is a threshold-exceedingvoltage change but that the battery voltage does not change often enoughto meet or exceed a rate of change threshold, the fuel gauge remains inits currently-enabled power mode. Finally, if the fuel gauge determinesthat there is at least one voltage change and that the greatest of thesevoltage changes meets or exceeds the voltage change threshold, andfurther if the fuel gauge determines that the battery voltage changesoften enough to meet or exceed a rate of change threshold, the fuelgauge switches to a higher power mode (unless the fuel gauge is alreadyin the highest available power mode, such as an active mode). Numerousvariations and permutations of this technique are contemplated andincluded within the scope of the disclosure.

In some embodiments, the sampling frequency may vary even within thesame fuel gauge power mode. For example, referring again to theforegoing example, if the fuel gauge determines that there is anincrease in voltage variation (i.e., greater voltage swings betweensamples and/or a greater percentage of samples indicating voltagechanges), but the voltage variation is not significant enough to warrantswitching modes, the fuel gauge may remain in its currently-enabledpower mode but it may increase or decrease its sampling frequency toaccount for the increased variation in battery voltage.

FIG. 1 is a front view of an illustrative consumer electronic device. Invarious implementations, the consumer electronic device 100 implementsthe systems and methods described herein. The electronic device 100 maybe any suitable device that uses a battery (e.g., a lithium ionbattery). Non-limiting examples of such electronic devices include smartphones (e.g., APPLE iPHONE®, SAMSUNG GALAXY NOTE®), tablets (e.g., APPLEiPAD®, AMAZON KINDLE®), laptops, video cameras (including camcorders),and handheld game consoles (e.g., SONY PLAYSTATION VITA®). Other suchdevices are contemplated and included within the scope of thisdisclosure. The illustrative consumer electronic device 100 includes adisplay screen 102 that is preferably a touch screen. It furtherincludes various tactile input devices 104, such as buttons arranged invarious locations around the exterior of the electronic device 100.Additional input and output devices, such as microphones and speakers,also may be incorporated within such a device.

FIG. 2 is a block diagram of at least some components within theelectronic device 100. The electronic device 100 includes anapplication-specific integrated circuit (ASIC) 200 comprising processinglogic 202 (e.g., a microprocessor), storage 206 coupled to theprocessing logic 202 and comprising software code 204 (e.g., anoperating system or applications), input features 208 (e.g., buttons,touch screen, microphone), output features 210 (e.g., display screenthat may be the same as the touch screen, speaker, haptic feedbackmotor), and a network interface 212 for communicating with other devices(e.g., via the Internet). Other components may be included on the ASIC200. The ASIC 200 is powered by a battery pack (“battery”) 214. A fuelgauge 216 couples to the battery 214. In at least some embodiments, theASIC 200, the fuel gauge 216 and the battery 214 couple to each other ina parallel configuration, so that the ASIC 200 may receive power fromthe battery 214 while the fuel gauge 216 monitors the output of thebattery 214. Further, in some embodiments the ASIC 200 may be replacedby a plurality of ASICs or other circuitry. The techniques disclosedherein may be implemented in any electronic device in which any suitabletype of load (here, the ASIC 200) is powered by the battery 214. Inoperation, and as described in greater detail with respect to FIG. 3,the fuel gauge 216 monitors the voltage output by the battery 214. Asexplained above, the fuel gauge 216 autonomously selects its own powermode based on the battery voltage fluctuation—that is, based on thebattery voltage swings between samples as well as the frequency withwhich the battery voltage changes.

FIG. 3 is a block diagram of at least some components within a fuelgauge 216 of the electronic device 100. The block diagram of FIG. 3 isconceptual in nature, meaning that at least some of the blocks representfunctions performed by the various parts of the electronic device 100.The actual circuit logic used to implement the functions represented bythe blocks may vary depending on design considerations and preferencesand will be readily known to or determined by one of ordinary skill inthe art.

Still referring to FIG. 3, the battery 214 contains a voltage source 300that creates a potential across terminals 302, 304. The terminal 302provides a voltage to node 318, which couples to the fuel gauge 216 andto the ASIC 200. The terminal 304 couples to ground and to node 320,which couples to the fuel gauge 216 and the ASIC 200. The fuel gauge 216comprises voltage detection logic 306, a programmable voltagefluctuation level register 308, mode control logic 310, a clock 312 andport 314, and a sampling timer 316. The programmable register 308contains the voltage change threshold value and the rate of changethreshold value, described above. In operation, the voltage detectionlogic 306 samples the voltage present at node 318 (i.e., the batteryvoltage) at a sampling frequency that varies according to thecurrently-enabled mode of the fuel gauge 216. In at least someembodiments, when the fuel gauge 216 is in a standby mode, the voltagedetection logic 306 may sample the battery voltage once per minute; in arelaxed mode, once every 20 seconds; in an operating mode, once every 10seconds; and in an active mode, four times per second, although thescope of disclosure is not limited to these sampling frequencies foreach power mode, nor is the scope of disclosure limited to the use of asingle sampling frequency in individual power modes.

If, upon consecutively sampling the voltage a predetermined number oftimes, the logic 306 determines that the voltage has not changed at all,the fuel gauge 216 switches to a lower power mode. If the logic 306determines that the voltage has changed, but not by the voltage changethreshold stored in the register 308, or if the logic 306 determinesthat the voltage has changed by the voltage change threshold but thatthe voltage has not changed as often as required by the rate of changethreshold, the logic 306 concludes that there is not enough variation inthe battery voltage to warrant an upward power mode switch, and itremains in its currently-enabled power mode. If, however, the logic 306determines that the battery voltage has changed by the voltage changethreshold, and if the logic 306 further determines that the voltage haschanged often enough (by any suitable amount, or by some additionalminimum threshold programmed into the register 308) to meet or exceedthe rate of change threshold, the logic 306 issues a signal to the modecontrol logic 310 to increase the power mode of the fuel gauge 216.

FIG. 4 is a graph 400 illustrating a variable frequency voltage samplingscheme. The graph 400 plots different power modes on the x-axis 402 andpower level on the y-axis 404. Specifically, graph 400 shows a standbymode 406, a relaxed mode 408, an operation mode 410, and an active mode412. During the standby mode 406, the power level 414 is relatively low;during the relaxed mode 408, the power level 416 is increased; duringthe operation mode 410, the power level 418 is further increased; andduring the active mode 412, the power level 420 is highest. The samplingfrequency at which the fuel gauge samples the battery voltage variesamong these power modes. During standby mode 406, numeral 422 indicatesa relatively low sampling frequency; during relaxed mode 408, numeral424 indicates an increased sampling frequency; during the operation mode410, the sampling frequency 426 is further increased; and during theactive mode 412, the sampling frequency 428 is relatively high.Specific, illustrative sampling frequencies are provided above and thusare not reproduced here.

FIG. 5 is a flow diagram of an illustrative method 500 usable toimplement the techniques disclosed herein. The method 500 begins bydetermining a current fuel gauge power mode (step 502). The method 500includes performing a sampling operation in the current power mode (step504). A sampling operation is a sampling of the battery voltage apredetermined number of times at a predetermined sampling frequency,where the sampling frequency is determined based at least on the currentpower mode of the fuel gauge. The method 500 then includes determiningwhether the results of the sampling operation met the criteria forincreasing the fuel gauge power mode (step 506). If so, the fuel gaugeautonomously increases its power mode (step 508). Otherwise, the method500 comprises determining whether the results of the sampling operationmet the criteria for decreasing the fuel gauge power mode (step 510). Ifso, the fuel gauge autonomously decreases its power mode (step 512).Otherwise, the currently-enabled power mode is maintained. Control ofthe method 500 then returns to step 504, as is the case after completionof steps 508 and 512. The method 500 may be modified as desired—forexample, to include additional steps, delete steps, or rearrange steps.

Referring to FIG. 6, a block diagram of select components within anelectronic device is illustrated. The electronic device may include apower side 602 and a system side 604. The power side includes a battery606 and may include a fuel gauge 608. The fuel gauge 608 is coupled tothe battery 606 through a power line 610. In this manner, the fuel gauge608 may monitor the voltage output of the battery 606 through the powerline 610 while the battery powers the system side 604. The system side604 may include one or more processors 612 coupled to the battery 606through the power line 610. The fuel gauge 608 may be configured tooperate in a plurality of power modes corresponding to varying samplingfrequencies of the battery. In various implementations, the fuel gaugemay be configured to operate in a stand-by mode, a relax mode, amoderate mode, and a normal mode. In other implementations, the fuelgauge may be configured to operate in more than four or less than fourmodes. In a particular implementation, the fuel gauge 608 may detectvoltage fluctuations from the battery caused by varying internalresistance of the battery 606.

Referring to FIG. 7, a graph illustrating a variable frequency voltagesampling scheme as it relates to a battery's internal resistance andvoltage fluctuation is illustrated. As illustrated, the system includesvarying modes 702 relating to the power level 704 being provided by thebattery. As illustrated by FIG. 7, the system may include a sleep mode706, a relax mode 708, an operation mode 710, and an active operationmode 712. In various implementations, the varying modes of the systemcorrespond with fluctuation of the voltage in the power line. Asillustrated by FIG. 7, the fluctuation of the voltage 714 may be stablewhen the system is in a sleep mode or relax mode, and may increase andbecome less stable as the power level of the system, or current drawnby/provided to the system, increases. The amount of voltage fluctuation720 may be highest in an active operation mode of the system. In variousimplementations, the fuel gauge monitors the amount of voltagefluctuation and estimates the system's operation mode. The system'soperation may include a sleep mode 706, a relax mode 708, an operationmode 702, and an active operation mode 712. In various implementations,the fuel gauge is configured to optimize its sample rate in accordancewith the estimated mode. The fuel gauge may include a plurality of modescorresponding to the operation modes of the system. More specifically,the fuel gauge may include a stand-by mode 722 corresponding to thesleep mode 706, a relax mode 724 corresponding to the relax mode 708, amoderate mode 726 corresponding to the operation mode 702, and a normalmode 728 corresponding to the active operation mode 712. Further, eachmode of the fuel gauge may correspond with a sampling rate of the outputpower of a battery by the fuel gauge. Each of the lines 718 indicates avoltage sample from the power line. As illustrated, the fuel gaugecurrent 716 may be minimal in a stand-by mode and in turn, the voltagemay be rarely sampled in the stand-by mode 722 of the fuel gauge. As thevoltage fluctuation on the power line increases (or the power level ofthe system increases) the fuel gauge may increase its mode and samplethe voltage of the battery at an increased frequency. While the graph ofFIG. 7 illustrates the fuel gauge as having four power modes, a stand-bymode, a relaxed mode, a moderate mode, and a normal mode, variousimplementations of fuel-gauges may have more or less power modes thanfour which may correspond to the varying levels of fluctuation of abattery's voltage, and in turn, a corresponding power level of thesystem.

Referring to FIG. 8, a diagram representing the voltage fluctuation of asystem is illustrated. As illustrated, the voltage fluctuation 802 is acombination of the open circuit voltage (V_(OCV)) 804 and the internalvoltage (V_(internal)) 806 of the battery 808. V_(internal) is basedupon the internal resistance of the battery as the voltage is a productof the internal resistance and the current being provided by thebattery. In various implementations, V_(OCV) 804 may remain constant orsubstantially constant. Accordingly, the voltage fluctuation may bedirectly proportional to V_(internal) 806 as the voltage fluctuation 802is caused by the battery's internal resistance.

Referring to FIG. 9, a block diagram of select components within animplementation of a fuel gauge of an electronic device is illustrated.As illustrated, the fuel gauge 902 includes a voltage sensor 904. Thevoltage sensor 904 is configured to repeatedly sample measured powervalues or voltage values from the power line 906 coupled to the battery908. The voltage sensor 904 may sample the voltage at any samplingfrequency disclosed herein. In various implementations, though notillustrated by FIG. 9, the fuel gauge 902 may include a current sensorconfigured to repeatedly sample a current from the battery. The fuelgauge may also include a temperature sensor configured to repeatedlysample a temperature of the battery. Similarly, in variousimplementations, though not illustrated by FIG. 9, the fuel gauge mayinclude an analog-to-digital converter (ADC). The ADC may be used toconvert any analog signals from any sensors (whether or not disclosedherein) into digital signals. The fuel gauge 902 includes a memory 910which may be coupled to the voltage sensor 904. Internal resistance data(IDD) corresponding to the battery may be stored in the memory 904. Invarious implementations, the internal resistance data may be in the formof a plurality of relative state of charge (RSOC) values. The RSOCvalues may indicate the charge capacity of the battery. While the RSOCof a new battery is the actual state of charge of the new battery, asbatteries age, among other things, the RSOC value or capacity decreasesas the internal resistance increases. Related V_(OCV) values may also bestored with the RSOC values, or the RSOC values may indicate associatedV_(OCV) values.

In various implementations, the RSOC values stored in the memory may becalculated using a Coulomb counting method. In such implementations,Coulomb counting may keep track of the amount of Coulombs extractedfrom/inserted into the battery and may compute the RSOC as a ratio ofremaining Coulombs and battery capacity. The basic technique for Coulombcounting may be based on equation 1, with Q equaling capacity, Iequaling resistance, and t equaling time.

Q(Li)=∫I(t)dt  Equation 1

In other implementations, the RSOC values may be calculated using avoltage tracking method. In such implementations, the RSOC values may bedetermined by a capacitance of the battery which may be determined bydetecting a voltage of the battery and looking up the voltage valueusing table of voltage-capacity graphs in order to determine thecorresponding capacity of the battery based on the voltage value.

In various implementations, the memory 910 may include a plurality oftemperature parameters. The temperature parameters may includecorrective factors corresponding to a temperature of the batterynecessary to calculate the true internal resistance. As illustrated byFIG. 9, in various implementations the fuel gauge 902 may include atemperature sensor 912 coupled with the memory 910. The temperaturesensor 912 may be configured to detect the temperature of the battery908. While the temperature sensor 912 is illustrated as directly coupledto the memory 910, in other implementations the temperature sensor maybe directly coupled to the processor 914. By knowing the temperature ofthe battery 908, more accurate RSOC values may be calculated by thesystem in various implementations.

In various implementations, the RSOC values and/or the temperatureparameters may be used to calculate a plurality of internal resistancevalues that correspond with varying internal resistances of the battery908. While the implementations disclosed herein discuss the use of RSOCvalues and/or temperature parameters, in other implementations otherdata may be stored in the memory 910 which may be used to calculate aninternal resistance of the battery 908. Further, the data stored in thememory may be variable based upon specific applications. Thus, invarious implementations the RSOC data (or other data) put into thememory may vary depending on, among other things, the type of thebattery. Examples of different types of batteries that may alter thedata stored in the memory may include, by non-limiting example, prismbatteries, cylinder batteries, polymer batteries, and any other type ofbattery. Data relating to manufacturer-specific characteristics of eachbattery type may also be stored in the memory. Once data has been storedin the memory, the data may be rewritten as needed. In variousimplementations, an external system may be able to alter the data in thememory based on, by non-limiting example, the kind of battery, thebattery manufacturer, and/or the application that the battery is beingused for. In other implementations, the fuel gauge may be able to detectthe battery being used and may either directly set the parameters and/ordata in the memory that need to be used with that battery or instruct anexternal system to set the parameters and/or data in the memory to beused with that battery.

Still referring to FIG. 9, the fuel gauge 902 includes a processor 914coupled with the memory 910. The processor 914 may be used to calculatea plurality of threshold values. The threshold values may be calculatedby multiplying the plurality of internal resistance values derived fromthe RSOC values and/or temperature parameters/values with a current ofthe system. The threshold values calculated may be used to determine thesampling frequency with which the fuel gauge should sample the voltageof the battery. While the processor 914 and the memory 910 areillustrated as two separate and distinct components in FIG. 9, invarious implementations the processor and memory may be included in asingle component.

The fuel gauge 902 may also include a fluctuation monitor block 916. Thefluctuation monitor block may track the fluctuation of the voltagesbeing detected by the voltage sensor 904. Accordingly, the fluctuationmonitor block 916 may implement the process of detecting the voltage ofthe system in real time. In particular implementations, the fluctuationmonitor block may determine how many times the fluctuation of thevoltage crosses the threshold voltage. In other implementations, theprocessor 914 may determine how many times the fluctuation of thevoltage crosses the threshold voltage. While the processor 914 and thefluctuation monitor block 916 are illustrated as two separate componentsin FIG. 9, in various implementations the processor 914 may be includedwithin the fluctuation monitor block 916.

In various implementations, the processor 914 may be configured tocompare the fluctuation of the voltages, or measured powers, sensed bythe voltage sensor with the plurality of threshold values derived fromthe data stored in the memory. In various implementations the fuel gaugeincludes mode control logic 918, and based upon the comparison of theactual fluctuation of the voltages with the plurality of thresholdvalues derived from the data stored in the memory, the mode controllogic may determine which power mode the fuel gauge is to operate in.More specifically, the mode control logic may determine whether the fuelgauge should operate in the same mode and sample the voltage of thebattery at the same frequency, operate in a less active mode and samplethe voltage of the battery at a lesser frequency, or operate in a moreactive mode and sample the voltage of the battery at an increasedfrequency. The sampling frequencies may include, by non-limitingexample, a zero sampling frequency, a low sampling frequency, a mediumsampling frequency, or a high sampling frequency.

In various implementations, the fuel gauge 902 includes a sampling timer920. The mode control logic 918 may communicate the mode the fuel gauge902 should be operating in to the sampling timer 920, and the samplingtimer 920 may in turn dictate the frequency of the sampling by thevoltage sensor 904. In this manner, the voltage sensor is configured torepeatedly sample the measured power being drawn by the load from thebattery at a sampling frequency corresponding to the power mode of thefuel gauge using the sampling timer. Accordingly, the fuel gauge 902 isconfigured to either increase, decrease, or maintain a samplingfrequency based upon a measured power being drawn by a load coupled tothe battery 908.

Referring to FIG. 10, a graph showing internal impedance/resistance of abattery is illustrated. As illustrated, the internal resistance of thebattery may remain constant through the battery's entire capacity lifecycle (or from 100% remaining capacity to 0% remaining capacity). Theinternal resistance may stay consistent by appropriately modifying thecurrent at particular SOC values. In this manner, appropriate voltagethresholds may be set for the implementations of thresholds disclosedherein. As an illustrative example, a high voltage threshold of 0.2volts may be set by multiplying the resistance of 0.2 ohms (asillustrated by FIG. 10) with 1 amp. Similarly, a medium threshold of 0.1volts may be set by multiplying 0.2 ohms with 0.5 amps. Likewise, a lowthreshold of 0.02 volts may be set by multiplying 0.2 ohms with 0.1amps.

Referring to FIG. 11, a graph showing varying internalimpedance/resistance of a battery is illustrated. In contrast with tothe graph of FIG. 10, a battery's internal resistance may varysignificantly across the battery's capacity life cycle. Alternatively,the graph may be characteristic of a particular battery's chemistry, anymay be characteristic of the battery's chemistry from its first use.

Referring to FIG. 12, a graph showing how internal impedance of abattery is affected by temperature is illustrated. As illustrated,varying temperatures of a battery may shift the internal resistance of abattery across the battery's capacity life cycle. More specifically, abattery at 0 degrees Celsius may have increased internal resistance ascompared to a battery at 10 degrees Celsius, and the battery at 10degrees Celsius may have increased internal resistance as compared to abattery at 25 degrees Celsius. As such, temperature parameters may benecessary in determining the threshold values based on internalresistance of a battery.

Referring to FIG. 13, a flow chart illustrating an implementation of amethod for how threshold values are determined is illustrated. Themethod may include inputting a plurality of RSOC values and/ortemperature parameters into a memory of a fuel gauge, as illustrated byblock 1302. The RSOC values may be obtained using any method disclosedherein. The RSOC values and/or temperature parameters may be stored in atable within a memory. The method of determining the threshold valuesmay include looking up the appropriate RSOC value and/or temperatureparameter as illustrated by block 1304. Upon obtaining this data, themethod may include calculating an internal resistance value as indicatedby block 1306. The internal resistance values may be calculated by aprocessor. The internal resistance may then be multiplied by a currentof the system, as illustrated by block 1308, in order to obtain avoltage threshold 1310. This may also be done by the processor.

Referring to FIG. 14, a flow chart illustrating an implementation of amethod of how the sampling frequency is determined, and in turn, animplementation of a method for conserving power, is illustrated. Themethod may include sampling at least two measured powers, which may bevoltages, from a power line coupled to a battery and determining afluctuation value between the measured powers sampled, as indicated byblock 1402. The fluctuation value may be determined by a fluctuationmonitor block. The sampling frequency of the voltage sensor may bedetermined by a sampling timer coupled with the voltage sensor. Thoughnot illustrated, the method may also include sensing a temperature ofthe battery through a temperature sensor included in the fuel gauge. Invarious implementations, more than two voltages, or measured powers, aresampled. In such implementations, a plurality of fluctuation values maybe generated not just for the continual monitoring of the battery, butalso to ensure that the fluctuation values are true fluctuation valuesand are not a result of noise.

In various implementations, the method may include storing a pluralityof RSOC values corresponding to a capacitance of the battery in amemory. The RSOC values stored may be generated using any methoddisclosed herein. Further, the method may include calculating aplurality of threshold values using the method taught by FIG. 13.

As illustrated, in various implementations, the method may then includedetermining, as illustrated by block 1404, whether there is a load,charge, or discharge based upon the value of the fluctuation. This maybe done by comparing the fluctuation value between the measured powerswith one or more threshold power measurements derived from a table ofvalues corresponding with the plurality of RSOC values of the batteryand/or the internal resistance values of the battery. The one or morethreshold power measurements may be derived according to the method setforth in FIG. 13. The method includes, using the fluctuation between theat least two measured power values, sending a signal using a processorof the fuel gauge to a mode control logic circuit to one of increase (ifthe fluctuation exceeds a necessary threshold), decrease (if thefluctuation fails to exceed the necessary threshold), or maintain (ifthe fluctuation exceeds one necessary threshold but not another) asampling rate of the fuel gauge. More specifically, if there is no load,the fuel gauge is instructed to enter a slow operation stage andcommunicate to the voltage sensor to enter into the zero frequencysampling mode. If, on the other hand, the fluctuation value indicatesthat there is a charge or discharge, the method includes determining ifthe power level of the fuel gauge should operate in a relaxed mode bydetermining whether or not the fluctuation value exceeds a predeterminedthreshold. If it doesn't exceed the predetermined threshold, then thefuel gauge is instructed to enter into an operation stage illustrated byblock 1410 and communicate to the voltage sensor to sample the voltageat a low sampling frequency mode corresponding to the relaxed mode ofthe fuel gauge. If, on the other hand, the fluctuation value exceeds thethreshold, then the fuel gauge does not enter into the relaxed mode butdetermines whether the fluctuation value exceeds a predeterminedthreshold associated with the moderate mode as indicated by block 1412.If the fluctuation value does not exceed the threshold associated withthe moderate mode, then the fuel gauge enters into the moderate mode, asindicated by block 1414, and communicates to the voltage sensor toincrease the sampling frequency a medium frequency sampling modeassociated with the moderate mode. If, on the other hand, thefluctuation value exceeds the threshold associated with the moderatemode, then it is determined that there is an active charge and the fuelgauge enters into a normal operation mode and communicates to thevoltage sensor to increase the sampling frequency to a high samplingfrequency mode.

As the voltage sensor continues to sample the voltage, it will continueto sense charges or discharges. If it senses discharges, or if thebattery is transitioning from an active operation mode to a less activeoperation mode, such as a relaxed mode, then the same method may be usedas outlined above to determine what the sampling frequency of thevoltage by the voltage sensor should be. In such implementations, as thefluctuation between the sampled measured power values decreases, thefluctuation value may be less than particular thresholds. In suchimplementations, the fuel gauge may then enter into lesser power modesassociated with less frequent sampling. In this manner the fuel gaugemay autonomously change the sampling period and conserve power by onlysampling the voltage of the battery as necessary.

As illustrated in the flow chart of FIG. 14, various currents areillustrated as associated with the various operation modes. It isunderstood that these currents could change as the various thresholdsare variable and customizable. Further, while the method illustrated byFIG. 14 illustrates four different power modes of the fuel gauge, it isunderstood that the method for conserving power may include the abilityof the fuel gauge to enter into more than or less than four differingpower modes.

In places where the description above refers to particularimplementations of fuel gauges and power conservation systems andimplementing components, sub-components, methods and sub-methods, itshould be readily apparent that a number of modifications may be madewithout departing from the spirit thereof and that theseimplementations, implementing components, sub-components, methods andsub-methods may be applied to other fuel gauges and power conservationsystems.

What is claimed is:
 1. A fuel gauge comprising: a voltage sensor coupled with a memory; a processor coupled with the memory; a mode control logic circuit coupled with the processor and the voltage sensor; and a sampling timer coupled with the mode control logic circuit and the voltage sensor; wherein the fuel gauge is configured to one of increase, decrease, or maintain a sampling frequency based upon a measured power being drawn by a load coupled to a battery.
 2. The fuel gauge of claim 1, wherein the fuel gauge is configured to one of increase or decrease the sampling frequency from one of a zero sampling frequency, a low sampling frequency, a medium sampling frequency, or a high sampling frequency.
 3. The fuel gauge of claim 1, wherein the memory comprises a plurality of RSOC values derived using a Coulomb counting method.
 4. The fuel gauge of claim 1, wherein the memory comprises a plurality of RSOC values derived using a voltage tracking method.
 5. The fuel gauge of claim 1, wherein the fuel gauge is configured to calculate a plurality of internal resistance values.
 6. The fuel gauge of claim 1, wherein the voltage sensor is configured to repeatedly sample the measured power being drawn by the load from a battery at a sampling frequency corresponding to a power mode of the fuel gauge using the sampling timer.
 7. The fuel gauge of claim 1, wherein the fuel gauge is configured to compare a fluctuation between a plurality of measured power values to one or more threshold values derived from a plurality of RSOC values comprised in the memory.
 8. The fuel gauge of claim 1, further comprising a fluctuation monitor block coupled to the voltage sensor.
 9. A fuel gauge comprising: a voltage sensor coupled with a memory; a processor coupled with the memory; a mode control logic circuit coupled with the processor and the voltage sensor; a temperature sensor coupled with the memory; and a sampling timer coupled with the mode control logic circuit and the voltage sensor; wherein the fuel gauge is configured to one of increase or decrease a sampling frequency based upon a measured power being drawn by a load from a battery.
 10. The fuel gauge of claim 9, wherein the fuel gauge is configured to one of increase or decrease the sampling frequency from one of a zero sampling frequency, a low sampling frequency, a medium sampling frequency, or a high sampling frequency.
 11. The fuel gauge of claim 9, wherein the memory comprises a plurality of RSOC values derived using a Coulomb counting method.
 12. The fuel gauge of claim 9, wherein the memory comprises a plurality of RSOC values derived using a voltage tracking method.
 13. The fuel gauge of claim 9, wherein the voltage sensor is configured to repeatedly sample the measured power being drawn by the load from the battery at a sampling frequency corresponding to a power mode of the fuel gauge using the sampling timer.
 14. The fuel gauge of claim 9, wherein the fuel gauge is configured to compare a fluctuation between two measured power values to one or more threshold values derived from a plurality of RSOC values comprised in the memory.
 15. A method of conserving power comprising: sampling at least two measured power values of a battery using a voltage sensor coupled with a sampling timer; determining a fluctuation between the at least two measured power values; comparing the fluctuation between the at least two measured power values to one or more threshold power measurements; and using the fluctuation between the at least two measured power values, sending a signal to a mode control logic circuit to one of increase, decrease, or maintain a sampling rate of a fuel gauge.
 16. The method of claim 15, further comprising sensing a temperature of the battery through a temperature sensor comprised in the fuel gauge.
 17. The method of claim 16, wherein the temperature of the battery is used to calculate the one or more threshold power measurements.
 18. The method of claim 15, wherein a sampling frequency comprises one of a zero sampling frequency mode, a low sampling frequency mode, a medium sampling frequency mode, or a high sampling frequency mode. 